<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style>
#b1{ width:810px;
margin:auto;}
#a1{width:800px; height:200px; background-color:#0C9; margin-bottom:20px; float:left; }
#a2{width:200px; height:600px; background-color:#9F3; margin-right:10px; float:left;}
#a3{width:590px; height:600px; background-color:#CC9; float:left;}
</style>
</head>

<body>
</body>
<div id="b1">
<div id="a1">我</div>
<div id="a2">我</div>
<div id="a3">我</div>
</div>


</html>
